From: Sudeep Holla <sudeep.holla@arm.com>
To: Sujeet Kumar Baranwal <sbaranwal@marvell.com>
Cc: linux-pm@vger.kernel.org,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
Sudeep Holla <sudeep.holla@arm.com>
Subject: Re: [EXT] Re: SCMI & Devfreq
Date: Thu, 19 Sep 2019 16:23:00 +0100 [thread overview]
Message-ID: <20190919152300.GA11801@bogus> (raw)
In-Reply-To: <BYAPR18MB2438047B622951C6EFE92FABAF8E0@BYAPR18MB2438.namprd18.prod.outlook.com>
(Adding linux-pm list)
On Wed, Sep 18, 2019 at 10:53:07PM +0000, Sujeet Kumar Baranwal wrote:
> Sudeep, One trivial question wrt SCMI-CPUFREQ framework.
>
> The SCMI perf protocol would tell what are different frequencies the
> platform support in the beginning.
>
> For example, the command :
> cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
> shows:
> 280000 560000 840000 1120000 1400000 1820000 1960000 2240000 2520000 2800000
>
> /* Attempt to change the frequency */
> ~ # echo 2240000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed
> It works.
>
> But in a scenario, where user tries a number which is not listed, SCP
> applies its own logic to get a nearby value frequency for CPU and returns.
>
> My question is that could we add some print message in kernel that user wish
> is not exactly fulfilled, an approximation has been done so the user
> explicitly knows his command has been partially met. If this to happen, a
> patch might be needed in kernel. What is your opinion?
>
May be, you need to check with the maintainers ? :)
The path of execution is:
cpufreq_set(policy, freq) [cpufreq_userspace.c]
__cpufreq_driver_target(policy, freq, CPUFREQ_RELATION_L) [cpufreq_userspace.c]
index = cpufreq_frequency_table_target(policy, target_freq, relation) [cpufreq.c]
__target_index(policy, index) [cpufreq.c]
So if you need logs, it needs to be in core file rather than individual
drivers.
--
Regards,
Sudeep
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next prev parent reply other threads:[~2019-09-19 15:23 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <BYAPR18MB24387C9DDE32067F1763B6DEAFB00@BYAPR18MB2438.namprd18.prod.outlook.com>
2019-09-13 10:23 ` SCMI & Devfreq Sudeep Holla
2019-09-16 5:22 ` [EXT] " Sujeet Kumar Baranwal
2019-09-16 10:15 ` Sudeep Holla
2019-09-16 17:36 ` Sujeet Kumar Baranwal
2019-09-18 22:53 ` Sujeet Kumar Baranwal
2019-09-19 15:23 ` Sudeep Holla [this message]
2019-10-07 18:20 ` Sujeet Kumar Baranwal
2019-10-14 16:58 ` Sudeep Holla
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